1. Field of Invention
The present invention relates to a machining center, and more particularly to a machining center with a relay tool exchange device.
2. Description of the Related Art
With reference to FIG. 10, a conventional machining center comprises a table (50′), two columns (51′), a crossbeam (52′), a spindle (53′), a tool magazine (60′) and a tool exchange device (54′). The table (50′) has two transverse sides. The columns (51′) are mounted respectively near the transverse sides of the table (50′). The crossbeam (51′) is mounted transversely on the columns (51′), is moveable relative to the table (50′) along the columns (51′) and has a tool end. The spindle (53′) is mounted on the crossbeam (52′), is moveable transversely along the crossbeam (52′) and has a spindle head and a machining tool. The machining tool is mounted detachably on the spindle head. The tool magazine (60′) is mounted near one of the columns (52′) and the tool end of the crossbeam (52′). The tool exchange device (54′) is mounted on the tool end of the crossbeam (52′).
When a machining process is completed and the machining tool of the spindle (52′) is changed, the spindle moves to the tool end of the crossbeam (52′) and the tool exchange device (54′) detaches the tool from the spindle (53′). Then the crossbeam (52′) moves down to dispose the tool exchange device (54′) adjacent to the tool magazine (60′) and the tool exchange device (54′) grips a new tool for a next machining process from the tool magazine (60′). After the new tool is gripped, the tool exchange device (54′) rotates 180 degrees and inserts the used machining tool into the tool magazine (60′) and mounts the new tool on the spindle head of the spindle (53′). Finally, the tool exchange device (54′) rotates to disengage from the spindle (53′), and the crossbeam (52′) moves up to perform the next machining process.
The conventional machining center as described has the following disadvantage:
1. When the machining tool on the spindle (53′) is changed, the crossbeam (52′) needs to move up and down and the travel is quite long and usually causes a large position error. Hence the conventional machining center with a high precision is hardly manufactured.
2. Because the position of the tool magazine (60′) is fixed, the crossbeam (52′) must move down to a predetermined position to change tools. Therefore, size of workpieces that can be machined by the conventional machining center is limited.
3. When the machining tool on the spindle (60′) is changed, the crossbeam (52′) must move down to the predetermined position. So the conventional machining center takes a long time to change tools and machining efficiency of the conventional machining center is low.
4. Because the tool magazine (60′) extends in a longitudinal direction, the size of the tool magazine (60′) and number of tools received in the tool magazine (60′) is limited. When some special machining processes are performed, some tools in the tool magazine need to be changed manually, and this increases time consumption.
To overcome the shortcomings, the present invention provides a machining center with a relay tool exchange device to mitigate or obviate the aforementioned problems.